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Holst H, Andresen K, Blom J, Højlyng N, Kemp M, Krogfelt KA, Christensen JJ. A Case of Helicobacter cinaedi Bacteraemia in a Previously Healthy Person with Cellulitis. Open Microbiol J 2008; 2:29-31. [PMID: 19088908 PMCID: PMC2593038 DOI: 10.2174/1874285800802010029] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2008] [Revised: 03/26/2008] [Accepted: 03/27/2008] [Indexed: 02/08/2023] Open
Abstract
Helicobacter cinaedi is an infrequent, but well recognized cause of gastroenteritis in immunosuppressed patients. Here we report a case of an extra-intestinal infection in a previous healthy 61-year old heterosexual male. Focus for the infection was most likely cellulitis on the lower right leg. The bacterium was cultured from blood twice within one week. Electron microscopy of the isolate visualized bipolar flagella. Partial DNA sequencing of the 16S rRNA gene and phenotypic characterization of the isolate established the species diagnosis. The patient was treated with rifampicin. After end of treatment blood cultures were negative and the cellulitis had disappeared.
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Abdul-Redha RJ, Prag J, Sonksen UW, Kemp M, Andresen K, Christensen JJ. Granulicatella elegans bacteraemia in patients with abdominal infections. ACTA ACUST UNITED AC 2007; 39:830-3. [PMID: 17701726 DOI: 10.1080/00365540701299624] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Bloodstream infections with Granulicatella (previous Abiotrophia) elegans are rare. A few reported cases were associated with infective endocarditis. Three cases of bacteraemia with G. elegans in patients who were operated for acute abdominal diseases are described. Abdominal foci should be considered when G. elegans is recovered from blood.
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Holst H, Hartmann-Petersen S, Dargis R, Andresen K, Christensen JJ, Kemp M. [Chancroid]. Ugeskr Laeger 2007; 169:2124. [PMID: 17553398] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Chancroid is caused by the bacterium Haemophilus ducreyi. It is a sexually transmitted disease causing a soft chancre with a necrotic base and purulent exudate. The incidence of this illness is very low in Denmark and is probably underestimated. The bacterium is very fragile in transport, and culture is often negative. The chance of demonstrating the bacterium is greatly enhanced by the use of molecular techniques. In this case, we report on a specific PCR test for H. ducreyi that was used to establish the diagnosis in a 40-year-old male.
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Kemp M, Christensen JJ, Kolmos HJJ, Andresen K. [Aptamers--new type of reagents to research, diagnostics and treatment]. Ugeskr Laeger 2007; 169:1136. [PMID: 17394847] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
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Christensen JJ, Andresen K, Justesen T, Kemp M. Ribosomal DNA sequencing: experiences from use in the Danish National Reference Laboratory for Identification of Bacteria. APMIS 2006; 113:621-8. [PMID: 16218938 DOI: 10.1111/j.1600-0463.2005.apm_224.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Diagnostic tools for identification of bacteria have developed dramatically in the last decade. Sequencing of genes coding for rRNA has led to revolutionary insights into the phylogeny and taxonomy of bacteria, and to new demands on the service provided by national reference laboratories for identification of bacteria. At the Danish Reference Laboratory for Identification of Bacteria, partial 16S rDNA sequencing has been used since 2001 to identify "difficult" strains submitted for taxonomic elucidation. Experiences relating to phenotypic as well as 16S rDNA sequencing of the first 175 strains examined are presented. Approximately 2/3 of the strains were Gram-positive and 1/3 Gram-negative. One fifth of the strains were anaerobic, while 4/5 were either facultatively anaerobic or aerobic. Methodological agreement was seen for most strains at species and/or genus level. Methodological disagreement was relatively rare. In 1/6 of the strains valuable information was obtained from sequencing results, while for some strains identification was based primarily on the phenotypic results. Only a few strains could not be clearly identified by either method. A very large number of strains representing taxons ranging from facultatively anaerobic to aerobic and anaerobic species and genera, Gram-positive as well as Gram-negative, were successfully examined. Of the submitted strains many have only rarely been encountered as human pathogens. Thus, genotypic identification may result in recognition of hitherto seldom recognized or unrecognized bacteria as human pathogens, which will lead to a better understanding of the nature of human infections. It is self evident that we should focus on slowly growing, fastidious or 'difficult' organisms when using sequencing for national reference purposes. Short sequences (450-650 base pairs) seem sufficient for most identifications. Molecular bacterial identification is a powerful tool for national reference laboratories, enhancing both the speed and validity of examinations performed.
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31
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Reinhard M, Prag J, Kemp M, Andresen K, Klemmensen B, Højlyng N, Sørensen SH, Christensen JJ. Ten cases of Actinobaculum schaalii infection: clinical relevance, bacterial identification, and antibiotic susceptibility. J Clin Microbiol 2005; 43:5305-8. [PMID: 16208004 PMCID: PMC1248514 DOI: 10.1128/jcm.43.10.5305-5308.2005] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Nine of 10 strains of Actinobaculum schaalii caused urinary tract infections in predisposed individuals. Identification included 16S rRNA gene sequence analysis and use of the API Coryne and Rapid ID 32 A test systems. A. schaalii is easily overlooked due to its slow growth in ambient air and its resemblance to the normal bacterial flora on skin and mucosa.
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32
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Heegaard NHH, Beyer NH, Kogutowska E, Tanassi JT, Jensen SM, Andresen K, Christensen JJ. [Botulinum and ricin toxins]. Ugeskr Laeger 2005; 167:3387-9. [PMID: 16159488] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Due to their acute toxicity, accessibility and history of use, ricin and botulinum toxins are at the present time the most relevant bioterror toxins. We give a brief review of their toxicity and possible uses in bioterror attacks and describe two cases in Denmark in which immunochemical, PCR and mass spectrometric assays developed in-house were used to confirm a foodborne botulinum toxin E case and to identify bovine serum albumin as the powder enclosed in a letter sent to the U.S. Embassy in Copenhagen.
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Christensen JJE, Andresen K, Kemp M. [New diagnostic methods for bacterial infections after the introduction of increased bioterrorism preparedness]. Ugeskr Laeger 2005; 167:3416-7. [PMID: 16159496] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
Bacillus anthracis, Francicella tularensis, Yersinia pestis, Burkholderia pseudomallei and Brucella melitensis are the bacteria most often mentioned in connection with possible biological terrorist acts. It is known that these microorganisms can be cultured and weaponised for such a purpose. This survey provides examples of the use of diagnostic methods for those microorganisms, further detailed in relation to establishing a national center for biological preparedness in Denmark.
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Christensen JJ, Kilian M, Fussing V, Andresen K, Blom J, Korner B, Steigerwalt AG. Aerococcus urinae: polyphasic characterization of the species. APMIS 2005; 113:517-25. [PMID: 16086822 DOI: 10.1111/j.1600-0463.2005.apm_183.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A polyphasic characterization of Aerococcus urinae is presented. In this study the intraspecies relationships between 26 strains of varying geographical origin were examined by phenotypic tests, ribotyping and multilocus enzyme electrophoresis. The results demonstrated two main phenotypic patterns that could be distinguished in tests for hydrolysis of aesculin, and acid production from amygdalin and salicin. Strains were either negative (n=19) or positive (n=6) in these tests. One strain had a deviating pattern. Heterogeneity within the 19 pattern I strains was demonstrated especially by phenotypic tests (acid production from ribose, mannitol, sorbitol, sucrose and D-arabitol) and by multilocus enzyme electrophoresis. However, DNA sequence analysis of the 16S rRNA (n=7) and gyrB genes (n=3) from strains representing the two main patterns showed no variation in sequences among strains. Comparison of A. urinae and representatives of related taxa by 16S rDNA sequence analysis showed that the taxon is related to, but distinct from, other Aerococcus spp.
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Kemp M, Holtz K, Andresen K, Christensen JJ. Demonstration by PCR and DNA sequencing of Corynebacterium pseudodiphtheriticum as a cause of joint infection and isolation of the same organism from a surface swab specimen from the patient. J Med Microbiol 2005; 54:689-691. [PMID: 15947436 DOI: 10.1099/jmm.0.45954-0] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
A case of infectious arthritis following arthroscopy is described. Real-time PCR, using universal bacterial primers targeting the 16S rRNA gene, and subsequent DNA sequencing of the PCR product demonstrated the presence of DNA from Corynebacterium pseudodiphtheriticum in the synovial fluid from the affected knee. Culture from a surface swab from the site of purulent discharge from the knee was initially reported as growing normal skin microbiota. Knowing the result of the DNA analysis, the specimen was re-examined and a diphtheroid bacterium was isolated. The DNA sequence of the isolated bacterium was identical to that of the DNA in the joint. The isolated bacterium was tested for susceptibility to relevant antibiotics. Demonstration and identification of bacterial DNA by PCR and gene sequencing may not by itself give information on important characteristics such as susceptibility to antibiotics of the infecting bacterium. The present case illustrates that the results obtained by the method can be used to isolate the relevant bacterium in culture from other sites and thereby characterize it. It furthermore demonstrates that C. pseudodiphtheriticum can cause severe arthritis when inoculated into joints.
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Wiese L, Nielsen X, Andresen K, Kjaer A, David K. 16S rDNA sequencing revealed Citrobacter freundii as the cause of liver abcess after banding of rectal haemorrhoids. J Infect 2005; 50:163-4. [PMID: 15667920 DOI: 10.1016/j.jinf.2004.08.027] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Andresen K, Balf D, Marcu CB. Massive pulmonary embolism in a patient with Streptococcus agalactiae tricuspid valve endocarditis. Heart 2005; 91:279. [PMID: 15710698 PMCID: PMC1768791 DOI: 10.1136/hrt.2004.038828] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
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38
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Pedersen S, Böcher S, Schiellerup P, Andresen K, Hertz B. [Tularemia acquired in Denmark by an eight-year-old child]. Ugeskr Laeger 2005; 167:773-4. [PMID: 15779266] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
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39
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Andresen K, Das R, Park HY, Smith H, Kwok LW, Lamb JS, Kirkland EJ, Herschlag D, Finkelstein KD, Pollack L. Spatial distribution of competing ions around DNA in solution. PHYSICAL REVIEW LETTERS 2004; 93:248103. [PMID: 15697865 DOI: 10.1103/physrevlett.93.248103] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2004] [Indexed: 05/11/2023]
Abstract
The competition of monovalent and divalent cations for proximity to negatively charged DNA is of biological importance and can provide strong constraints for theoretical treatments of polyelectrolytes. Resonant x-ray scattering experiments have allowed us to monitor the number and distribution of each cation in a mixed ion cloud around DNA. These measurements provide experimental evidence to support a general theoretical prediction: the normalized distribution of each ion around polyelectrolytes remains constant when ions are mixed at different ratios. In addition, the amplitudes of the scattering signals throughout the competition provide a measurement of the surface concentration parameter that predicts the competition behavior of these cations. The data suggest that ion size needs to be taken into account in applying Poisson-Boltzmann treatments to polyelectrolytes such as DNA.
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Kemp M, Andresen K, Sørensen M, Christensen JJ. [New diagnostics of infection: demonstration of bacterial DNA by polymerase chain reaction and identification by DNA sequencing]. Ugeskr Laeger 2004; 166:4351-4. [PMID: 15587624] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/01/2023]
MESH Headings
- Arthritis, Infectious/diagnosis
- Arthritis, Infectious/genetics
- Arthritis, Infectious/microbiology
- Bacterial Infections/diagnosis
- Bacterial Infections/genetics
- Bacterial Infections/microbiology
- Bacteriological Techniques
- Base Sequence
- DNA, Bacterial/genetics
- Endocarditis, Bacterial/diagnosis
- Endocarditis, Bacterial/genetics
- Endocarditis, Bacterial/microbiology
- Humans
- Meningitis, Bacterial/diagnosis
- Meningitis, Bacterial/genetics
- Meningitis, Bacterial/microbiology
- Polymerase Chain Reaction
- RNA, Ribosomal/genetics
- Sensitivity and Specificity
- Sequence Analysis, DNA
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Christensen CB, Jørgensen L, Jensen AT, Gasim S, Chen M, Kharazmi A, Theander TG, Andresen K. Molecular characterization of a Leishmania donovanii cDNA clone with similarity to human 20S proteasome a-type subunit. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1500:77-87. [PMID: 10564720 DOI: 10.1016/s0925-4439(99)00086-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Using plasma from patients infected or previously infected with Leishmania donovanii, we isolated a L. donovanii cDNA clone with similarity to the proteasome a-type subunit from humans and other eukaryotes. The cDNA clone, designated LePa, was DNA sequenced and Northern blot analysis of L. donovanii poly(A(+))mRNA indicated the isolation of a full length cDNA clone with a transcript size of 1.9 kb. The expressed recombinant LePa fusion protein induced proliferation of peripheral blood mononuclear cells in one out of seven patients who had suffered from visceral leishmaniasis. Plasma from 16 out of 25 patients with visceral leishmaniasis and four out of 18 patients with cutaneous leishmaniasis contained IgG antibodies which reacted with the purified LePa fusion protein as evaluated in an ELISA. The LePa DNA sequence was inserted into an eukaryotic expression vector and Balb/c mice were vaccinated. DNA vaccination of Balb/c mice with LePa generated an initial significant reduction in lesion size after challenge.
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MESH Headings
- Animals
- Antibodies, Protozoan/blood
- Base Sequence
- Blotting, Northern
- Blotting, Western
- Cloning, Molecular
- Cysteine Endopeptidases/genetics
- DNA, Complementary/genetics
- Enzyme-Linked Immunosorbent Assay
- Humans
- Leishmania donovani/genetics
- Leishmania donovani/immunology
- Leishmania donovani/isolation & purification
- Leishmaniasis, Visceral/immunology
- Leishmaniasis, Visceral/parasitology
- Leishmaniasis, Visceral/prevention & control
- Lymphocyte Activation/drug effects
- Mice
- Mice, Inbred BALB C
- Molecular Sequence Data
- Multienzyme Complexes/genetics
- Proteasome Endopeptidase Complex
- Recombinant Fusion Proteins/immunology
- Recombinant Fusion Proteins/pharmacology
- Sequence Analysis, DNA
- Sequence Homology, Amino Acid
- Vaccines, DNA/immunology
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42
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Andresen K, Christensen CBV, Jørgensen L, Jensen ATR, Kemp M, Kharazmi A, Theander TG. Construction of DNA vaccines against Leishmaniasis. Parasitol Int 1998. [DOI: 10.1016/s1383-5769(98)81075-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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43
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Andresen K, Gasim S, Elhassan AM, Khalil EA, Barker DC, Theander TG, Kharazmi A. Diagnosis of visceral leishmaniasis by the polymerase chain reaction using blood, bone marrow and lymph node samples from patients from the Sudan. Trop Med Int Health 1997; 2:440-4. [PMID: 9217699] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
We have evaluated the sensitivity of the polymerase chain reaction (PCR) as a diagnostic tool for Leishmania donovani using blood, bone marrow and lymph node samples from Sudanese patients with a confirmed infection. Forty patients were diagnosed by microscopic examination of bone marrow or lymph node samples. The PCR was able to detect parasite DNA in 37 out of 40 blood samples. In bone marrow and lymph node samples, the PCR was able to detect parasite DNA in all 7 and 6 samples, respectively. We suggest that the PCR should be considered as a valuable and sensitive tool for the diagnosis of L. donovani infection. However, if PCR diagnosis is to supplement or even replace microscopic diagnosis in developing countries, a large number of patients with no apparent signs of infection and patients with other diseases have to be tested in order to evaluate its true potential.
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Andresen K, Gasim S, Elhassan AM, Khalil EAG, Barker DC, Theander TG, Kharazmi A. Diagnosis of visceral leishmaniasis by the polymerase chain reaction using blood, bone marrow and lymph node samples from patients from the Sudan. Trop Med Int Health 1997. [DOI: 10.1046/j.1365-3156.1997.d01-293.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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45
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Andresen K, Gasim S, Elhassan AM, Khalil EAG, Barker DC, Theander TG, Kharazmi A. Diagnosis of visceral leishmaniasis by the polymerase chain reaction using blood, bone marrow and lymph node samples from patients from the Sudan. Trop Med Int Health 1997. [DOI: 10.1111/j.1365-3156.1997.tb00166.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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46
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Yu Q, Andresen K, Osten W, Jueptner W. Noise-free normalized fringe patterns and local pixel transforms for strain extraction. APPLIED OPTICS 1996; 35:3783-3790. [PMID: 21102775 DOI: 10.1364/ao.35.003783] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Noise reduction is one of the most exciting problems in automatic fringe processing. We propose a two-dimensional (2-D) envelope transform for normalization of fringe patterns, coupled with spin filtering, to construct so-called noise-free normalized fringe patterns. The 2-D envelope transform uses correct fringe intensity envelopes for normalization of fringe patterns, i.e., for making the fringe background and amplitude constant over the whole field. Spin filtering is applied to fringe patterns for removal of random noise taking into account fringe flow. With spin filtering and the 2-D envelope transform, a noise-free normalized fringe pattern is constructed for postprocessing. Based on this improved fringe pattern, two local pixel transforms for strain extraction from a single moiré pattern are developed, in which the digital pure secondary moiré method is improved and the strain-field image method with division is developed.
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Andresen K, Gaafar A, El-Hassan AM, Ismail A, Dafalla M, Theander TG, Kharazmi A. Evaluation of the polymerase chain reaction in the diagnosis of cutaneous leishmaniasis due to Leishmania major: a comparison with direct microscopy of smears and sections from lesions. Trans R Soc Trop Med Hyg 1996; 90:133-5. [PMID: 8761571 DOI: 10.1016/s0035-9203(96)90112-1] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
We have compared the sensitivity of the polymerase chain reaction (PCR) as a diagnostic tool against conventional microscopical diagnostic techniques in patients with cutaneous leishmaniasis from the Sudan. Twenty-eight patients were diagnosed according to clinical criteria followed by microscopical examination of histological sections and slit or impression smears. The PCR had a sensitivity of 86% when used alone, and 93% when combined with Southern blotting. In contrast, microscopy of histological sections had a sensitivity of 76% and slit and impression smears of only 55% and 48%, respectively. The PCR should be considered as a valuable and sensitive diagnostic tool in the diagnosis of cutaneous leishmaniasis; it has the added advantage of identification of the species of Leishmania causing the lesion.
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Andresen K, Ibrahim ME, Theander TG, Kharazmi A. Random amplified polymorphic DNA for the differentiation of Leishmania donovani isolates from Sudan. Trans R Soc Trop Med Hyg 1996; 90:204-5. [PMID: 8761592 DOI: 10.1016/s0035-9203(96)90142-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
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49
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Yu Q, Andresen K. Fringe-orientation maps and fringe skeleton extraction by the two-dimensional derivative-sign binary-fringe method. APPLIED OPTICS 1994; 33:6873-6878. [PMID: 20941234 DOI: 10.1364/ao.33.006873] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The fringe-orientation information of an interferometric fringe pattern is provided in the form of a fringe-orientation map by spin filtering. The fringe-orientation information is an important feature of fringe patterns and is helpful in many fringe-pattern processing algorithms. With the help of a fringe-orientation map the two-dimensional derivative-sign binary-fringe method is developed to extract fringe skeletons from a fringe pattern with an arbitrary fringe distribution. This fringe skeleton extraction method does not require thresholds and a thinning process. It is relatively robust and highly accurate.
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50
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Yu Q, Liu X, Andresen K. New spin filters for interferometric fringe patterns and grating patterns. APPLIED OPTICS 1994; 33:3705-3711. [PMID: 20885762 DOI: 10.1364/ao.33.003705] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
The basic spin filter for interferometric fringe patterns is improved and developed into several new versions for different applications. These spin filters can filter off random noise efficiently and have almost no blurring effect and phase distortion for the fringe patterns. First, they find the local fringe tangent direction, and then they apply a one-dimensional low-pass filter on this direction. In this way the spin filters can separate easily and clearly high-frequency noise from a real fringe signal with nearly zero frequency. The new spin filters are suitable not only for various fringe patterns but also for wrapped-phase, line-grating, and cross-grating patterns, which are impossible by common filters.
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